Fluid mixing

ABSTRACT

An apparatus for mixing two or more fluids including a series of passages into each of which each fluid to be mixed can be passed at a chosen rate so that each passage can supply a chosen mixture, and valve means operable to select which of the passages is used to supply the mixture.

United States Patent 1191 Cox Aug. 20, 1974 FLUID MIXING 3,308,6193/1967 Richardson et al 137/599 x 3,542,064 11/1970 0 11 137 599 x [75]Inventor Lawrence Alfred 3,603,349 9 1971 1375599 x England 3,677,2967/1972 Berger 137/606 [73] Assignee: The British Oxygen Company Limited,London, Engkmd Primary ExaminerRobert G. Nllson Attorney, Agent, orFirmDennison, Dennison,

[22] Filed: Nov. 14, 1972 Townshend & Meserole [21] Appl. No.: 306,184

[57] ABSTRACT 52 11.5.0. 137/599, 137/606 An apparatus for mixing two ormore fluids including 51 Int. Cl. Fl6k 19/00 a series of 1199991698 intoeach of which each fluid to be [58] Field Of Search 137/599, 607, 606mixed can be passed at a Chosen rate 89 that each P sage can supply achosen mixture, and valve means [56] References i d operable to selectwhich of the passages is used to sup- UNITED STATES PATENTS Ply3,032,053 5/1962 Ross 6161. 137/607 x 8 Claims, 1 Drawing Figure Thepresent invention relates to fluid mixing, and particularly to apparatusfor mixing gases for medical purposes.

In order to provide a comprehensive gas supply service for respiratorypurposes it is necessary to be able to provide a mixture of twodifferent gases in which the constituent gases may be present in any oneof several different ratios. It has been customary to provide such amixture by using a gas mixing apparatus which can provide continuousvariation in the composition ratio of the mixture over a considerablerange. This apparatus is relatively complex, and hence, expensive.

It is an aim of the invention to provide a fluid mixing apparatus whichis relatively simple in construction. Accordingly the present inventionprovides an apparatus for mixing two or more different fluids which isas claimed in the appended claims.

The present invention will now be described by way of example withreference to the accompanying drawing which is a schematic flow diagramof apparatus for producing an air-oxygen mixture for a lung ventilator.

Referring to the drawing, oxygen and air are passed along theirrespective inlet lines 1 and 3 to regulators 2 and 4 respectively at apressure of 0.4N/mm These regulators are designed and fluid loaded toensure that the oxygen and air leave their respective regulators at aconstant pressure of O.28N/mm The oxygen passes from regulator 2 alongthe inlet line and is directed into four separate flow lines, 6, 8, land 12. The air leaves the regulator 4 and is directed along the inletline 3 into four flow lines l4, 16, 18 and 20. All the flow lines areconnected to an outlet line 21 at a common outlet point 22.

Before reaching the outlet point 22, the oxygen lines 6, 8, and arejoined to the air lines 16, 18 and respectively. Flow impedances in theform of calibrated orifices 26 are located in the flow lines 6, 8, 10,16, 18 and 20. These orifices (or throttles) are dimensioned so thattheir flow impedances have such relative magnitudes as to be able togive from the pairs of flow lines 6 and 16, 8 and 18 and 10 and 20,mixtures containing percent, percent and 60 percent by volume of oxygen,respectively. It will be appreciated that there will be 100 percent andapproximately 20 percent of oxygen in the flow lines 12 and 14respectively because the line 12 is an oxygen line and the line 14 is anair line.

Push button on/off switches 28, 30, 32, 34 and 36 are located in theflow lines as shown in the drawing. The switches 30, 32 and 34 controlthe mixed pairs of flow lines 6 and 16, 8 and 18, and 10 and 20respectively.

Non-return valves 38 are located in all the flow lines downstream of theon/off switches to prevent reversed gas flow.

The outlet line 21 leads from the outlet point 22 to the lung ventilator(not shown). An outlet regulator is located in the outlet line 21. Anoff/on switch 42 and a calibrated orifice 44 are located in the outletline 21 downstream of the outlet regulator 40. The bore of the orifice44 defines the gas flow rate to the ventilator.

The operation of the apparatus is as follows:

The oxygen and air supplies are turned on, and the switch 42 is switchedoff. The appropriate one of the on/off switches 28 to 36 is pressed toselect a gas of the required composition.

At the start of each inspiratory phase of the ventilator, the switch 42is switched on by the flow mechanism of the ventilator. This allows theselected gas to pass through the orifice 44 to the ventilator.

At the end of each inspiratory phase, the switch 42 is switched off bythe ventilator flow mechanism thereby shutting off the inspiratory gassupply to the ventilator until the start of the next inspiratory phase.

The composition of the gas being fed to the ventilator can be changedsimply by pressing the appropriate one of the switches 28 to 36 so as toopen the required flow line or pair of flow lines. The action ofpressing one of these on/off switches automatically releases apreviously pressed switch so as to close the previously opened flow lineor pair of flow lines. This prevents two flow lines or pairs of flowlines from being open at the same time so as to pass a gas of incorrectcomposition.

In this particular apparatus, the gas is fed from the outlet regulator40 at a pressure of 0.2N/mm Although non-return valves 38 are includedin this de' scribed apparatus, it is to be understood that apparatusaccording to the invention may operate efficiently without non-returnvalves.

The orifices 26 and 44 may be replaced by orifices of adjustablecross-sectional area. The calibrated orifice 44 may be replaced byeither a demand valve, or a fine adjustment valve which allows a presetadjustable gas flow. The fine adjustment valve may be used either withor without a flowmeter.

In a modified apparatus provision may be made for two or more of theon/off switches to remain on at the same time. This increases the numberof gas composition ratios which can be selected by an operator.

I claim:

1. A gas mixing apparatus including:

a. at least two gas inlet passages for the gases to be mixed;

b. a gas pressure regulator in each inlet passage;

0. a plurality of gas mixture distribution passages;

d. a plurality of flow rate control passages, each flow rate controlpassage being connected between an inlet passage and a gas mixturedistribution passage, and each gas mixture distribution passage beingconnected by flow rate control passages to both of said at least two gasinlet passages;

e. a calibrated flow impedance in each flow rate control passage, forpassing gas at a chosen flow rate to the gas mixture distributionpassage downstream thereof, whereby gas mixtures of different chosencompositions are able to be formed in the gas mix-,

ture distribution passages;

f. a common outlet to which all the gas mixture distribution passagesare connected, and from which a gas mixture can be supplied; and

g. valve means operable to close selected gas mixture distributionpassages, whereby the composition of the gas mixture supplied from thecommon outlet depends on which of the gas distribution passages is leftopen to the passage of gas therethrough.

2. Apparatus as claimed in claim 1, in which each flow impedance is inthe form of an orifice.

let switch in the outlet line downstream of the pressure regulator.

7. Apparatus as claimed in claim 5, including an orifice of reducedcross-sectional area downstream of the pressure regulator in the outletline.

8. Apparatus as claimed in claim 5, including a demand valve downstreamof the pressure regulator in the outlet line.

1. A gas mixing apparatus including: a. at least two gas inlet passagesfor the gases to be mixed; b. a gas pressure regulator in each inletpassage; c. a plurality of gas mixture distribution passages; d. aplurality of flow rate control passages, each flow rate control passagebeing connected between an inlet passage and a gas mixture distributionpassage, and each gas mixture distribution passage being connected byflow rate control passages to both of said at least two gas inletpassages; e. a calibrated flow impedance in each flow rate controlpassage, for passing gas at a chosen flow rate to the gas mixturedistribution passage downstream thereof, whereby gas mixtures ofdifferent chosen compositions are able to be formed in the gas mixturedistribution passages; f. a common outlet to which all the gas mixturedistribution passages are connected, and from which a gas mixture can besupplied; and g. valve means operable to close selected gas mixturedistribution passages, whereby the composition of the gas mixturesupplied from the common outlet depends on which of the gas distributionpassages is left open to the passage of gas therethrough.
 2. Apparatusas claimed in claim 1, in which each flow impedance is in the form of anorifice.
 3. Apparatus as claimed in claim 1, in which each flowimpedance has associated with it a non-return valve for each of thefluids passed to it.
 4. Apparatus as claimed in claim 1, in which thecross-sectional area of at least one of the orifices is adjustable. 5.Apparatus as claimed in claim 1 including a pressure regulator locatedin the outlet line.
 6. Apparatus as claimed in claim 5, including anoutlet switch in the outlet line downstream of the pressure regulator.7. Apparatus as claimed in claim 5, including an orifice of reducedcross-sectional area downstream of the pressure regulator in the outletline.
 8. Apparatus as claimed in claim 5, including a demand valvedownstream of the pressure regulator in the outlet line.